Understory Response to Tree Harvesting in Pinyon-juniper Woodlands

Download or read book Understory Response to Tree Harvesting in Pinyon-juniper Woodlands written by Richard L. Everett and published by . This book was released on 1984 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understory species associations and their association with tree species were examined on three intensively studied stands. We studied the chronosequence of understory species associated with different aged singleleaf pinyon (Pinus monophylla Torr. and Frem.) trees. Mid- to late pinyon-juniper understory succession was found to be more spatial than floristic in nature. Plants of the same species but occurring on different soil microsites responded differently to increasing tree competition. Succession was a plant by plant process rather than a linear replacement series of species at the population level. Phytosociological changes were documented following tree harvesting on 15 widely separated singleleaf pinyon-Utah juniper (Juniperous osteosperma [Torr.] Little) stands. Pre- and post harvest plant assemblages from the same site appeared in the same phytosociological groupings 80% of the time as defined by discriminate analysis. We suggest initial post harvest response was short term cyclic rather than successional and therefore more predictable. Post harvest seed rain suggested understory species have increased reproductive potential following tree harvest and can rapidly reoccupy disturbed sites. Survival strategies of individual species determined the quantitative character of seed rain Seed rain and subsequent seedling establishment were not the primary causes of increased understory cover following tree harvest. Remnant plants provided the initial cover increase. Post harvest cover rapidly increased for two years on the three intensively studied sites, but rate of increase declined during the following two year period. Soil microsites associated with the tree canopy produced greater grass yields than soils in the interspace between trees. Percent nitrogen and phosphorus increased in most grass species following tree harvest. Because of increased soil nutrient concentrations under the tree canopy we anticipated higher nutrient level in associated grass plants, but were unable to demonstrate this difference because of the dilution effects from increased yields. Soil nutrients were concentrated under the tree crown but were not distributed similarly with depth. Mineralizable-N, PO4, Zn, Mn, Cu, and Fe, accumulated in surface horizons. Total soluble salts, Ca, Mg, Na, and K accumulated in subsurface horizons. Nutrient enrichment in soils under the canopy was suggested to confer a competitive advantage to the tree species.